How the Shinkeijime Fish Spike and Ikijime Process Preserve Fish Freshness
Japan's Prime Method To Humanely Kill A Fish
Japan loves it’s fish and have come up with methods to not just preparing it, but also in preserving it. Sashimi itself has strict regulations towards freshness or else it can’t be served.
The Shinkeijime derives it’s name from the Japanese word of “ikijime” which translated means “to kill alive.” It is made of a stainless steel wire that is used to pierce into the fish’s brain and through the spinal cord to both kill and paralyze it.
The problem found with the traditional way of killing a fish, bashing or suffocating, are that they put a lot of stress on the fish before death, causing unnecessary chemical reactions within it that cause the fish to lose it’s flavor. Japan came up with a solution in the Shinkeijime.
How Does The Shinkeijime Keep Fish Fresh
When judging the level of freshness for fish, it is crucial to judge the level of ATP, or adenosine triphosphate within it. ATP is the compound that all living things produce for energy. And when that level lowers, lactic acid builds up which affects the taste of the fish.
Even after death, very fresh fish still have neurons fully intact that cause muscle spams even if they have been knocked on the head. However, by piercing through the spinal cord with the Shinkeijime, it also paralyzes the fish by destroying the neural network, preventing those reactions from happening. This is important for keeping the integrity of the fish’s natural flavor to preserving it’s ATP levels post-rigor.
Just how much of a difference does the Shinkeijime make?
Here is a comparison of two flounder fillets done for research by the University of Hokkaido comparing the ikijime method.
Both fish were left to preserve in ice water, the fish on the right that the Shinkeijime was used on has considerably less blood spread onto the muscles caused by the random muscle spams after death. This results in the fish having a cleaner meat, as well as a more robust flavor.
For more information on preserving your fish, read our article on Tips For Preserving Fish Freshness!